diff options
Diffstat (limited to 'contrib/ipfilter/man/ipnat.5')
| -rw-r--r-- | contrib/ipfilter/man/ipnat.5 | 147 |
1 files changed, 95 insertions, 52 deletions
diff --git a/contrib/ipfilter/man/ipnat.5 b/contrib/ipfilter/man/ipnat.5 index 2bedd0c..7db3308 100644 --- a/contrib/ipfilter/man/ipnat.5 +++ b/contrib/ipfilter/man/ipnat.5 @@ -1,3 +1,5 @@ +.\" $NetBSD$ +.\" .TH IPNAT 5 .SH NAME ipnat, ipnat.conf \- IP NAT file format @@ -7,45 +9,47 @@ The format for files accepted by ipnat is described by the following grammar: .nf ipmap :: = mapblock | redir | map . -map ::= mapit ifname ipmask "->" dstipmask [ mapport ] mapoptions. -map ::= mapit ifname fromto "->" dstipmask [ mapport ] mapoptions. -mapblock ::= "map-block" ifname ipmask "->" ipmask [ ports ] mapoptions. +map ::= mapit ifname lhs "->" dstipmask [ mapicmp | mapport | mapproxy ] + mapoptions . +mapblock ::= "map-block" ifname lhs "->" ipmask [ ports ] mapoptions . redir ::= "rdr" ifname ipmask dport "->" ip [ "," ip ] rdrport rdroptions . -dport ::= "port" number [ "-" number ] . -ports ::= "ports" number | "auto" . -rdrport ::= "port" number . +lhs ::= ipmask | fromto . +dport ::= "port" portnum [ "-" portnum ] . +ports ::= "ports" numports | "auto" . +rdrport ::= "port" portnum . mapit ::= "map" | "bimap" . fromto ::= "from" object "to" object . ipmask ::= ip "/" bits | ip "/" mask | ip "netmask" mask . dstipmask ::= ipmask | "range" ip "-" ip . +mapicmp ::= "icmpidmap" "icmp" number ":" number . mapport ::= "portmap" tcpudp portspec . mapoptions ::= [ tcpudp ] [ "frag" ] [ age ] [ clamp ] . -rdroptions ::= [ tcpudp | protocol ] [ rr ] [ "frag" ] [ age ] [ clamp ] . +rdroptions ::= rdrproto [ rr ] [ "frag" ] [ age ] [ clamp ] [ rdrproxy ] . -object :: = addr [ port-comp | port-range ] . -addr :: = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] . +object :: = addr [ port-comp | port-range ] . +addr :: = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] . port-comp :: = "port" compare port-num . port-range :: = "port" port-num range port-num . +rdrproto ::= tcpudp | protocol . rr ::= "round-robin" . age ::= "age" decnumber [ "/" decnumber ] . clamp ::= "mssclamp" decnumber . -tcpudp ::= "tcp/udp" | "tcp" | "udp" . +tcpudp ::= "tcp/udp" | protocol . +mapproxy ::= "proxy" "port" port proxy-name '/' protocol +rdrproxy ::= "proxy" proxy-name . protocol ::= protocol-name | decnumber . -nummask ::= host-name [ "/" number ] . -portspec ::= "auto" | number ":" number . +nummask ::= host-name [ "/" decnumber ] . +portspec ::= "auto" | portnumber ":" portnumber . +port ::= portnumber | port-name . +portnumber ::= number { numbers } . ifname ::= 'A' - 'Z' { 'A' - 'Z' } numbers . -number ::= numbers [ number ] . numbers ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' . .fi .PP -In addition to this, # is used to mark the start of a comment and may -appear at the end of a line with a NAT rule (as described above) or on its -own lines. Blank lines are ignored. -.PP For standard NAT functionality, a rule should start with \fBmap\fP and then proceeds to specify the interface for which outgoing packets will have their source address rewritten. @@ -101,41 +105,12 @@ or as map de0 from 10.1.0.0/16 to any -> 201.2.3.4/32 .fi .LP -For even greater control, one may negate either of the "from" or "to" clauses -with a preceding exclamation mark ("!"). Please note that one may not use a -negated "from" within a \fBmap\fP rule or a negated "to" within a \fBrdr\fP -rule. Such a rule might look like the following: -.LP -.nf -+map de0 from 10.1.0.0/16 ! to 10.1.0.0/16 -> 201.2.3.4/32 -.fi -.PP Only IP address and port numbers can be compared against. This is available with all NAT rules. -.SH COMMAND QUALIFIERS -At the end of each rule, a number of qualifiers can be used to change how -the rule works. They are as follows: -.TP -protocol -A specific protocol may be given either by its name (as found in -/etc/protocols) or its number. A special case for supporting both -TCP and UDP is allowed with the name \fBtcp/udp\fP. -.TP -.B round-robin -Once a rule with this term has been successfully used, it is put at the -bottom of the list of those available so that each one will get used, in -turn, in a list of matching left hand sides. -.TP -.B frag -This qualifier is currently has no impact on NAT operation. -.TP -.B age -If more refined timeouts are required than those available globally for -NAT settings, this allows you to set them for \fBnon-TCP\fP use. .SH TRANSLATION .PP To the right of the "->" is the address and port specification which will be -written into the packet providing it has already successful matched the +written into the packet providing it has already successfully matched the prior constraints. The case of redirections (\fBrdr\fP) is the simplest: the new destination address is that specified in the rule. For \fBmap\fP rules, the destination address will be one for which the tuple combining @@ -149,13 +124,76 @@ the packet will not be translated. The \fBmap-block\fP is more limited in how it searches for a new, free and unique tuple, in that it will used an algorithm to determine what the new source address should be, along with the range of available ports - the IP address is never changed and nor does the -port number ever exceed its alloted range. +port number ever exceed its allotted range. +.SH ICMPIDMAP +.PP +ICMP messages can be divided into two groups: "errors" and "queries". ICMP +errors are generated as a response of another IP packet. IP Filter will take +care that ICMP errors that are the response of a NAT-ed IP packet are +handled properly. +.PP +For 4 types of ICMP queries (echo request, timestamp request, information +request and address mask request) IP Filter supports an additional mapping +called "ICMP id mapping". All these 4 types of ICMP queries use a unique +identifier called the ICMP id. This id is set by the process sending the +ICMP query and it is usually equal to the process id. The receiver of the +ICMP query will use the same id in its response, thus enabling the +sender to recognize that the incoming ICMP reply is intended for him and is +an answer to a query that he made. The "ICMP id mapping" feature modifies +these ICMP id in a way identical to \fBportmap\fP for TCP or UDP. +.PP +The reason that you might want this, is that using this feature you don't +need an IP address per host behind the NAT box, that wants to do ICMP queries. +The two numbers behind the \fBicmpidmap\fP keyword are the first and the +last icmp id number that can be used. There is one important caveat: if you +map to an IP address that belongs to the NAT box itself (notably if you have +only a single public IP address), then you must ensure that the NAT box does +not use the \fBicmpidmap\fP range that you specified in the \fBmap\fP rule. +Since the ICMP id is usually the process id, it is wise to restrict the +largest permittable process id (PID) on your operating system to e.g. 63999 and +use the range 64000:65535 for ICMP id mapping. Changing the maximal PID is +system dependent. For most BSD derived systems can be done by changing +PID_MAX in /usr/include/sys/proc.h and then rebuild the system. .SH KERNEL PROXIES .PP IP Filter comes with a few, simple, proxies built into the code that is loaded into the kernel to allow secondary channels to be opened without forcing the -packets through a user program. -.SH TRNSPARENT PROXIES +packets through a user program. The current state of the proxies is listed +below, as one of three states: +.HP +Aging - protocol is roughly understood from +the time at which the proxy was written but it is not well tested or +maintained; +.HP +Developmental - basic functionality exists, works most of the time but +may be problematic in extended real use; +.HP +Experimental - rough support for the protocol at best, may or may not +work as testing has been at best sporadic, possible large scale changes +to the code in order to properly support the protocol. +.HP +Mature - well tested, protocol is properly +understood by the proxy; +.PP +The currently compiled in proxy list is as follows: +.HP +FTP - Mature +.HP +IRC - Experimental +.HP +rpcbind - Experimental +.HP +H.323 - Experimental +.HP +Real Audio (PNA) - Aging +.HP +IPsec - Developmental +.HP +netbios - Experimental +.HP +R-command - Mature + +.SH TRANSPARENT PROXIES .PP True transparent proxying should be performed using the redirect (\fBrdr\fP) rules directing ports to localhost (127.0.0.1) with the proxy program doing @@ -226,7 +264,13 @@ map ppp0 172.192.0.0/16 -> 209.1.2.0/24 portmap tcp/udp auto .fi .PP which would result in each IP address being given a small range of ports to -use (252). The problem here is that the \fBmap\fP directive tells the NAT +use (252). In all cases, the new port number that is used is deterministic. +That is, port X will always map to port Y. +WARNING: It is not advisable to use the \fBauto\fP feature if you are map'ing +to a /32 (i.e. 0/32) because the NAT code will try to map multiple hosts to +the same port number, outgoing and ultimately this will only succeed for one +of them. +The problem here is that the \fBmap\fP directive tells the NAT code to use the next address/port pair available for an outgoing connection, resulting in no easily discernible relation between external addresses/ports and internal ones. This is overcome by using \fBmap-block\fP as follows: @@ -241,7 +285,6 @@ own. As opposed to the above use of \fBmap\fP, if for some reason the user of (say) 172.192.0.2 wanted 260 simultaneous connections going out, they would be limited to 252 with \fBmap-block\fP but would just \fImove on\fP to the next IP address with the \fBmap\fP command. -.SH FILES /dev/ipnat .br /etc/services |
